Why does a red fox scream?

A red fox gives a siren-like shriek when approached by a more dominant fox. A more drawn-out "waaaaah" sound is believed to be used by females calling to males.

Foxes can make sounds ranging over five octaves. They bark when approaching each other and whine as a greeting. Adults make huffing noises when greeting their kits. Foxes also make sounds described as purrs, trills and chirps. Much fox communication takes place through facial expressions, postures and ear and tail positions. Foxes also communicate by scent marking with urine, feces, anal sac secretions and secretions from glands around the lips, jaws and foot pads.